1. Field of the Invention
The present invention relates to a camera module and a portable terminal provided with the camera module.
2. Description of the Related Art
A camera module having the function of autofocusing (AF) and/or zooming used for a portable terminal such as a mobile telephone is required to be constructed small in size.
When a camera module having an autofocusing (AF) function and/or zooming function is reduced in size, it is required to reduce the size of zoom lenses and the number of constituent parts. However, the zoom lenses must be moved in the direction of the optical axis of the lenses in order to change the focal distance thereof. Therefore, it is necessary to secure as long traveling distance of lenses as possible in a small space, and to downsize lens holders for retaining lenses and the moving mechanism or driving mechanism thereof. A variety of devisal are required to downsize the camera module while keeping easiness of assembling and adjusting.
As a camera module like this, there is disclosed a camera for example in Japanese Laid-Open Patent Application No. 7-63970 (hereafter referred to as patent literature 1), in which a cylindrical cam located at the side of the optical system of the camera is driven by a motor to move a lens holder for zooming and a lens holder for focusing. In Japanese Laid-Open Patent Application No. 2003-258971 (hereafter referred to as patent literature 2) is disclosed a camera module with zooming function for integrated into a mobile telephone, which is composed such that a lens holder for zooming and a lens holder for focusing are driven by rotating by hand a cylindrical cam partially exposing outside of the mobile telephone at the side face of the portion where optical system is accommodated.
Further, in Japanese Laid-Open Patent Application No. 6-214194 (hereafter referred to as patent literature 3) is disclosed a lens barrel on the inside surface of which is located a light shielding plate in a state deformed elastically. In Japanese Laid-Open Utility Model Application 4-65305 (hereafter referred to as patent literature 4) is disclosed a lens barrel on the inside surface of which is located a light shielding plate.
In Japanese Laid-Open Patent Application No. 10-62852 (hereafter referred to as patent literature 5) is disclosed a driving mechanism of camera which is provided with a motor which serves both for film feeding and autofocusing and a motor for zooming in order to perform the driving for autfocusing and the driving for feeding film in the opposite direction by a single driving motor with a simple construction constructed at a low cost, in which the transmission of the driving force of the motor serving both for film feeding and autofocusing is switched by means of planetary gear type clutches in the state of film winding and film feeding and in the state of film rewinding, and in which a gear for autofocus-driving is located where it can mesh with one or other of the planetary gear drives of the planetary gear type clutches, the position of one of the planetary gear is retained in the state it meshes with the gear for autofocus-driving with the limiting member and the limiting member being driven by the projecting and subtracting action of the zooming system in order to allow the limiting member to retain the driving system in the state that autofocus-driving is possible.
Further, in Japanese Laid-Open Patent Application No. 10-39401 (hereafter referred to as patent literature 6) and in Japanese Laid-Open Utility Model Application Publication No. 7-1438 (hereafter referred to as patent literature 7) is disclosed to aim to reduce noise and vibration a motor mounting structure in which the motor is sandwiched and fixed with a pair of ribs and vibration is absorbed by providing an elastic member on the periphery of the motor, and a structure in which the motor is fixed with screws by way of vibration absorbing members.
There are also known a motor mounting structure in which the periphery of the motor is bonded by means of a double-stick tape to the inside face of a motor holder which is formed by combining a base part and motor attaching wall in a general shape of letter “L” and the base part of the motor holder is fixed to the camera body by means of screws.
As a camera module, there are known one which is downsized by locating a lead screw for autofocusing and a lead screw for zooming on one side of the case and making it possible to assemble lenses from one side of the lens barrel of the camera module (hereafter referred to prior art 1), and one in which switching between telephotographing and macro-photographing in pan-focus lenses is done by means of a cylindrical cam located adjacent to lens frames (hereafter referred to prior art 2).
Further, there are known a lens moving mechanism for utilizing the space of lens barrel efficiently, in which a supporting part of the guide of lens frames is provided in a housing retaining a subject side lens and lens frames for zooming and focusing are driven by means of two lead screws (hereafter referred to prior art 3); a lens moving mechanism for configuring the lens barrel in small size, in which are provided a lead screw for zooming in the first quadrant around the optical axis, a lead screw for focusing in the second quadrant, and a guide shaft for guiding lens frames in the third quadrant (hereafter referred to prior art 4); a lens moving mechanism in which a subject side lens is retained in a upper housing, lens frames for zooming and focusing are driven by two lead screws respectively, bearings for the two lead screws and two guide shafts of the lens frames are provided in the upper housing, and CCD is attached to a lower housing (hereafter referred to prior art 5), and a camera module in which a light shielding cover is provided to cover the part where the lead screw mechanism for moving lenses is mounted (hereafter referred to prior art 6).
Further, as the downsizing of camera module for a portable terminal advances, the driving motor becomes small and the attaching of the motor becomes difficult as mentioned before. To resolve the problem, a composition is known in which a cylindrical step motor is located effectively in an lens-barrel to reduce the thickness of the lens-barrel and the lenses can be driven accurately and at high speed (hereafter referred to prior art 7). According to this prior art, the front lens group is located fixedly in the front side of the aperture position in the lens-barrel, the rear lens group is formed to have its lower part removed, a shutter consisting of two blades which are driven to open and shut in a range not interfere with the removed portion, the shutter serving both as the aperture, and the cylindrical step motor is located astride of the aperture position in the space below the rear lens group and front lens group.
Further, a composition is known in which, in order to construct a camera module to be thin and furthermore to realize accurate focusing and image zooming by moving lens position, lenses are fixed to the first and second barrel so that the lenses for focusing an image to an image pickup device do not deviate, further the first and second barrel are fixed to the housing, a guide groove is formed on one side of the housing to receive the extended part of the first and second housing so that the first and second housing can be slid (hereafter referred to as prior art 8). In the prior art 8, the rotation of the gear connected to the rotation shaft of the motor is converted to vertical and horizontal motion and the distance between the first barrel and the second barrel is adjusted.
However, the device disclosed in patent literature 1 is related to a camera module for a video camera, gives no consideration to downsize it to be installed in a portable terminal, a drive motor is located remote from the optical system in an ample space inside the camera module, and the motor is mounted at a position apart from the optical system with an efficient space secured. The device disclosed in patent literature 2 is related to a small sized camera module to be integrated in a portable terminal, etc., but it is manual operation type and can not be applied to a camera module in which zooming and autofocusing are performed by means of a motor.
The structure disclosed in patent literature 3, 4 is for providing a light shielding plate and not informative as structure for downsizing a camera module.
According to the driving mechanism disclosed in patent literature 5, it is required to provide two motors, i.e. a motor which serves both for film feeding and autofocusing and a motor for zooming, resulting in an increased size as a camera module to be equipped to a portable terminal.
Patent literature 6 and 7 each discloses a structure for mounting a driving motor of relatively large size and aims to reduce noise and vibration, not relates to a structure for mounting a small motor with good accuracy. To fix the motor to the motor holder by means of an adhesive agent and fix the motor holder by means of bolts as disclosed results in increased size of parts around the motor, in increased number of parts, and in increased cost.
Prior art 1 and 4 aims to downsize the camera module, but lead screws are provided separately for autofocussing and zooming, so the camera module inevitably increases in size. The camera module of prior art 2 is of pan-focus type and not informative for a module with an autofocusing function incorporated.
According to prior art 3, the space of lens barrel is utilized efficiently, however, it is featured only in that the subject side lens is retained in the housing thereof and the supporting part of the lens frames is provided in the housing, a driving device such as a motor is not integrated, and it is difficult to find it informative for composing a camera module. According to prior art 5, a driving mechanism and CCD are attached to separate housings and assembly process becomes complicated, so that they can not serve as a useful reference for composing a small sized camera module.
With prior art 7, the structure is complicated and the assembling of camera module becomes difficult. In a small camera module equipped to a portable terminal, each of the constituent parts is very small. Therefore, when a cylindrical step motor is located astride of the aperture position in the space below the rear lens group and front lens group, it is very hard and vexatious to mount and fix the cylindrical step motor to the housing of the camera module.
In prior art 8, there is no description about steps of procedure of assembling the camera module. Considering that each of the constituent parts is very small in a small camera module equipped to a portable terminal, work operation of assembling the camera module becomes very complicated depending on the relation of position of the first and second barrel.